Four years ago, Ireland’s lack of back-ups hurt them when it mattered most.
Deprived of Paul O’Connell, Peter O’Mahony and Johnny Sexton through injury for their quarter-final against Argentina, Joe Schmidt’s side were found wanting and succumbed to another last-eight exit.
The head coach has made no secret of the fact that this time around, he believes Ireland are much better placed to cope with any absentees.
There has been a concerted effort to build strength in depth and foster competition for places over this last four-year cycle.
And with what appears to be a mounting injury list, that claim will get its first big test on Saturday in their World Cup opener in Yokohama.
Against their perennial Guinness Six Nations rivals Scotland, Ireland will have to rely on strength in numbers.
If you want to get an idea of quite how strong this Ireland squad is, it is perhaps informative to consider who isn’t in the Far East.
Sean O’Brien and Dan Leavy were ruled out months ago through injury. British and Irish Lions like Simon Zebo and Jack McGrath were overlooked as were international stalwarts like Devin Toner, Kieran Marmion and Jordi Murphy.
You could put together the bones of a serious international side just from Schmidt’s off cuts.
Competition for places just to make the plane has never been higher, and Ireland now have a squad prepared for nearly every eventuality.
And so, with a mounting injury list this week that has seen Robbie Henshaw ruled out, Rob Kearney in serious doubt and Keith Earls in a race against time, Schmidt still has enviable options.
No Henshaw? No worries, in comes Garry Ringrose – one of the classiest No.13s in world rugby and long-labelled Brian O’Driscoll’s heir apparent.
No Kearney? Fear not, Jordan Larmour – one of the rising stars of Irish rugby with 16 caps and four Test starts at full-back – can slot straight in.
No Earls? That’s OK, how about a proven international winger in Andrew Conway with six tries in nine Test starts.
Indeed, you can go down the entire squad list and see that Ireland have built a base never before seen on the Emerald Isle.
Their stand-ins stand out.
Part of this is down to the wear and tear of international rugby, injuries mean new faces get blooded. Some sink and some swim.
But take the openside flanker position for example, any side in world rugby would be worried if players of the class of Leavy and O’Brien went down on the eve of the World Cup.
But Josh van der Flier is world-class in his own right, twice already an All Black conqueror in his young Test career, and a more than capable replacement.
O’Mahony, Stander and Rhys Ruddock could all do a job there as well, and have in the past.
Where Ireland maybe used to have a top-class starting XV, now their depth extends beyond even the 31 out in the Far East.
What about the half-backs, for so long the preserve of Messrs Sexton and Murray?
Joey Carbery is back fit and a rival for Sexton the like of which Ireland have not had since Ronan O’Gara hung up his boots.
And that is not to mention Jack Carty who has so impressed in his cameos since Schmidt gave him his head earlier this year.
And at No.9? Ok, Murray remains the class act, but injuries have limited him in the last year and again contenders have emerged.
Luke McGrath is a European champion and the heartbeat of an all-conquering Leinster side while Marmion and John Cooney are just a plane ride away if needed.
On the face of things, Ireland are more than ready to cope with whatever the next few weeks throw their way.
Lessons have been learned and replacements ready-made.
But the rehearsals are one thing. The real deal is around the corner, and Schmidt will have to hope that practice has indeed made perfect in the white-hot heat of a Rugby World Cup.